The invention relates to a method for regulating the fuel/air ratio of an internal combustion engine, the output signal from a first lambda probe, which is arranged in the exhaust duct of the internal combustion engine upstream of a catalyst, being supplied to the controller, and the controller emitting a manipulated variable for the fuel/air ratio, and there being supplied to the controller a correcting signal which is obtained from the output signal from a second lambda probe located downstream of the catalyst.
In order to achieve exhaust gases which are as free of pollutants as possible, regulating devices for internal combustion engines are known, in which the oxygen content in the exhaust duct is measured and evaluated. For this purpose, oxygen measuring probes, so-called lambda probes, are known, which operate, for example, on the principle of ionic conduction through a solid electrolyte as a result of an oxygen partial pressure difference and which emit, in accordance with the oxygen partial pressure prevailing in the exhaust gas, a voltage signal which has a voltage jump during the transition from oxygen deficiency to oxygen excess, and vice versa.
The output signal from the lambda probe is evaluated by a controller which, in turn, adjusts the fuel/air mixture via an actuator.
The primary aim of regulating the fuel/air ratio is to reduce harmful components of the exhaust gas emission of internal combustion engines.
With the aid of a second lambda probe, which is arranged downstream of the catalyst, the signal from the first lambda probe is corrected, since the probe is subject to aging phenomena.
Despite this superposed regulation, the aging phenomena of the first lambda probe cannot be corrected sufficiently.